Preparation of alpha-naphthol



Patented Feb. 19, 1935 v L I UNITED .S'I'ATES ENT- OFFICE 1,992,154" u 1 PREPARATION or ALPllA-NAPHTHOL Edgar C. Britton and Wesley C. Stoesser, Midland," Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan l No Drawing; Application November 10, 1932, i 1 1 Serial No. 642,021

2 Claims. (C1. zen-154) The invention relates to methods for the prepmaterially lower temper'aturethan would other aration of alpha-naphthol. wise be required thereby avoiding the formation The preparation of alpha-naphthol is ordinaof isomeric naphthols, and furthermore, that I rily effected by sulphonating naphthalene, treatiionapinaratus can be employed for carrying out 5 ing the mixture of isomeric naphthalene monothe hydrolysis, I I 5 sulphonic acids to form the sodium salts thereof, To the accomplishment of the foregoing and fusing the so-formed salts with sodium hydroxrelated ends, the invention, then, consists of the ide, acidifying the products of the fusion with method hereinafter fully described and particusulphuric acid or carbon dioxide, and separating larly pointed out inthe claims, the following dethe alpha-naphthol from the reaction mixture by scription setting forth in detail several-modes of 10 distillation with superheated steam. However, carrying out the invention/such disclosed modes since both alphaand beta-naphthols' are illustrating, however, but several of various ways formed in carrying out the foregoing process, and in which the principle of the invention may be since their boiling points are relatively close toused.

gether, i. e. 280 C. for the alphaand 286 C. The bromination of the naphthalene may be 15 for the beta-compound, there is occasioned concarried out at room temperature as by permitting siderable diiiiculty in the separation of the alphabromine to drip on naphthalene, or by brominat compound in pure form. ing the naphthalene in a suitable solvent, e. g.

The preparation of alpha-naphthol by the hyethylene chloride. The product of theforegoing drolysis of alpha-chloronaphthalene is disclosed bromination can then be hydrolyzed directly to in United States Patent 1,062,351. The condipure alpha-naphthol, without any isomeric betations under which the hydrolysis is accomplished naphthol being formed, at temperatures mateare set out as the treatment of alpha-chlororially lower than heretofore disclosed for the hy naphthalene with a 10 per cent aqueous caustic drolysis of mono-chloronaphthalene. The folsoda solution for 6 hours under pressure at a lowing examples serve to illustratethe results ob- 25 temperature of 280-300 C. A yield of 50-60 per tained by carrying out our novel method for the cent of alpha-naphthol is thereby obtained. In preparation of alpha-naphthol.

a pending application of Edgar C. Britten et al., Example 1 SerialNo. 454,303, filed May 21, 1930, it is disclosed that the chlorination of naphthalene al- A pp 100mb Was Charged with grams 0f ways yields i t of isomeric alphad; alpha-bromonaphthalene obtained by brominatbeta-chloronaphthalenes, the latter usually being p ha w u v t. a d 50 a s ing present in amount arying from 5 t 10 per of a 10 per cent aqueous sodium hydroxide solut, t is, t f apparent t t t hydroltion. The contents of the bomb were heated at ysis of the product formed by the chlorination a temperature of about for a Period 35 of naphthalene m t yield pure alphaof one hour. The bomb was then cooled and the naphthol t rather mixture of alpha... and contents removed. The filtrate was acidified with betapnaphthoh and t t t problem of tdilute sulphuric acid, cooled to room temperature ing the alphafrom the betaform still exists. and filtered. The crystals were dried, and dis- 40 Furthermore, t possibility of chlorinating tilled under an absolute pressure of 21 millimeters 40 naphthalene and separating the alpha-chloroof mercury at a temperature of fr to compound from the isomeric beta-compound berecover the T of f fore hydrolysis thereof is substantial eliminated alphana'phthol havmg meltmg pomt of because there is less than two degrees diffeb C. was 32.5 grams or 90.3 per cent of theoretical.

-ence in their boiling points. Example 2 In contrast to the foregoing, we have now found r i t run the same char 8 of that naphthalene can be brominated to yield pure gfi i g g gi g g was used but thegcom alpha'bromona'phthalene and that such alpha" centration of the sodium hydroxide solution was bromonaphthalene can be hydrolyzed directly in increased to 15 per cent. The reaction condi- 50 the presence of a copper-containing catalyst to tions, t is t apparatus temperature, time, give an exceptionally high yield of P p etc., were the same as in the preceding run. The naphthol. Moreover, we have found that the use yield of alpha-naphthol obtained was 92.4 per of said catalyst permits the hydrolysis of the cent of theoretical, and the melting point of the alpha-bromonaphthalene to be carried out at a compound was 934 C. 50

Emample 3 An iron bomb was charged with 69.0 grams of alpha-bromonaphthalene, 222.3 grams of a 15 per cent aqueous sodium hydroxide solution and 10.0 grams of cuprous oxide. The contents of the bomb were maintained at a temperature between 225 and 229 C. for a period of 6 hours. The bomb was then cooled, the contents removed and worked up substantially as described in Example 1. There was obtained 43.l grams of pure alpha-naphthol melting at 93.6 C., or an 89.8 per cent of theoretical yield. r

The preferred temperaturerangefor carrying out the hereinbefore described hydrolysis is between about and about 250 0., although higher temperatures may be used if desired, but, in general, they tend to produce some'beta-naphthol. In carrying out the hydrolysis in a copper bomb we have determined that temperatures as low as 180. C. may be used. but that a longer time is required for the, reaction to go to completion. Among the hydrolytic agents which we may substitute for thesodium hydroxide in the reaction are potassium hydroxide, calcium hydroxide, sodium carbonate, etc. The catalyst may be either metallic copper, or a copper compound, e. g. copper oxide, copper. chloride, etc. While we have described the use of dilute sulphuric acid for acidifying the product of the reaction be- (1) Exceptionally high yields of the desired product are obtained; (2) no isomeric betanaphthol is formed during the course of the reaction; (3) the low temperature at which the hydrolysis can be carried out permits the use 01' steam as the heating agent which is desirable as well as economical; and, (4) iron apparatus can be used for carrying out the hydrolysis and the copper catalyst does not have to be insulated therefrom.

Other-modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the details herein disclosed, provided the details stated by any of the following claims or the equivalent thereof be employed.

Wertherefore particularly point out and distinctly claim as our invention:-

1. In a method of preparing alpha-naphthol, the steps which consist in brominating naphthalene, reacting the product with an aqueous hydrolytic base under pressure at a temperature be-,

tween about180 C. and about 250 C. in the presence of a copper-containing catalyst, and separating alpha-naphthol from the reaction product. 7 2. In a method of preparing aIphanaphthol, the steps which consist inbrominating naphthalene, reacting under pressure the product with an aqueous hydrolytic' base at a temperature above about 180 C. in the presence of a coppercontaining catalyst, and of separating alphanaphthol from the reaction product.

EDGAR c. BRITTON. WESLEY, c. STOESSER. 

